225 



it or eise lack it. This is the Very limit of simplicity, and it 

 requires no special study to see that there is no corresponding 

 simplicity in the relation between a parent's final qualities and 

 those of its offspring. William Ritter has emphasized the impor- 

 tance of studying things as they are in biology, and not as they 

 might be, or ought to be on some or other theory. I fully agree 

 with this view, but I think we need never give up trying to 

 analyze complex processes like development into the different 

 fundamental factors which give this whole, simply besause neither 

 of these composing single things is by itself able to force its 

 simplicity upon the final result. 



In the study of development and evolution ; Mendelism now 

 takes a definite and extremely usefull place. 



Systematicians can be said to study the differences and 

 analogies between groups of organisms, each group homogeneous 

 for at least a great number of genetic factors, the Biometricians 

 are by Statistical methods studying the average effects of Variation 

 of both genetic and non- genetic factors in their combined result 

 on the Variation of the individuals within these groups. 



The biomechanists concern themselves with the interrelation 

 and Cooperation of genetic and non-genetic factors in the deve- 

 lopment of the organisms; experimental zoology and botany on 

 one hand, and Mendelism on the other ; may be conceived as 

 two special divisions of the study of biomechanism, experimental 

 zoology and botany being chiefly study of the non-genetic factors 

 in the development, and of environment on function ; Mendelism 

 being germinal analysis, the study of the genetic factors in the 

 development of the organisms. 



This we must always bear in mind, that we are studying 

 the genetic factors, their effect upon development, their nature, 

 the way in which they are transmitted, the possibility of their 

 being influenced, their relations toward one another, and that as 

 yet in this study we have not laid our hand on any of these 

 things, so that we must contend ourselves to notice the difference 

 it makes to a developing germ whether any one of them is present 

 or not. Thus, what we are actually regarding are differences 

 between individuals, and we are trying to find out, by carefully 

 planned breeding-experiments in how far these differences are 

 due to the presence or absence of each genetic factor. We have 

 abundant evidence that these genetic factors only act by influen- 



Verhandlungen des naturf. Vereineß in Brünn. XLIX. Band. 15 



